Method of reinforcing a concrete structure

ABSTRACT

A structural member for reinforcement of asphalt and concrete roadways and other products, and which includes a gridwork of warp strands and weft strands which are disposed at right angles to each other and so as to define an open structure. In one embodiment, the gridwork is impregnated with a thermosettable B-stage resin so as to interlock the strands at their crossover points and maintain the gridwork in a semi-flexible state, and after being applied to the product to be reinforced, the resin is heated to convert the same into a fully cured composite to thereby rigidize the gridwork and reinforce the product. In cases where the product to be reinforced is heated, such as asphalt paving, the heat of the product provides the heat necessary to fully cure the resin in situ. In another embodiment, the resin is fully cured to rigidize the gridwork prior to its being applied to the structure to be reinforced. A method of producing the resin impregnated gridwork is also disclosed.

CROSS-REFERENCE TO RELATED APPLICATION

This is a division of application Ser. No. 08/556,030, filed Nov. 19,1995, for STRUCTURAL REINFORCEMENT MEMBER AND METHOD OF UTILIZING THESAME TO REINFORCE A PRODUCT now U.S. Pat. No. 5,836,715.

FIELD OF THE INVENTION

The present invention generally relates to structural members adapted toreinforce a product. The present invention also relates to methods ofutilizing the structural member to form reinforced products.

BACKGROUND OF THE INVENTION

Traditional structures and products experience deterioration or failuresof various kinds which create a need for reinforcement. For example,roadways consisting of asphaltic concrete materials experiencedeterioration and failure over time in the form of reflective cracking,rutting, rolling up at traffic lights and "potholes". This deteriorationand failure of asphaltic concrete roadways require costly, frequent, andtime consuming repairs. Another family of products, concrete structures,such as columns, flat slabs, or constant cross-section shapes,deteriorate over time or as a result of seismic activity or needreinforcement for improved properties such as tensile strength. Variousapproaches have been investigated to address these problems byreinforcing the initial or existing products.

In regards to roadways, asphalt roadways are widely used, yet experiencefrequent and costly types of deterioration. Asphalt paving consists ofan asphalt compound combined with "rock aggregate". The aggregate addsto the compression strength of the asphalt with the asphalt compoundacting as a matrix to bind the road together. Asphalt roads deterioratemore quickly than concrete roads, and typical forms of deterioration are"reflective cracking", curling of the asphalt at places like stoplights,grooving of the asphalt due to repeated vehicular traffic following thesame path down the roadway and other cracking of the asphalt surface."Reflective cracking" is a major problem in asphalt overlays of existingconcrete roads or other road foundations. Reflective cracking occurswhere cracks in the existing concrete or asphaltic road or foundationpropagate from the existing road up through the new asphalt overlay.This requires costly repairs to otherwise new roads and attacks thestrength of the new overlay.

A variety of materials have been tried in the past to attempt to providereinforcement or stabilization for asphalt roadways. Several productscurrently seek to address the reflective cracking problem. One productis a non-woven overlay fabric or mat between a concrete road and anasphalt overlay called Petromat® from Amoco Fabrics and Fibers.Petromat® uses a random orientation of polypropylene fibers in a fabricmat that is laid down as a barrier between a road or road foundation andan asphalt overlay. The polypropylene does not have the modulus toresist expansion of concrete road in attempting to address the problemof reflective cracking. Also, the mat is of tight construction and doesnot allow asphalt or concrete to pass through the structure, insteadacting as a barrier between the layers. The mat is therefore notincorporated as a reinforcement structure throughout the new overlay.Instead, the mat acts only as a barrier which can wrinkle or fold inapplication. Further, a leveling or filling of cracks is necessarybefore using the Petromat ®.

Others have tried to use mesh structures of plastic materials and wovenfabrics to reinforce roadways. One product, Glasgrid® is a woven (leno)glass fiber fabric grid, coated with asphalt black coating with one sidehaving self-adhesive properties. Another product, Raupave® is a geogridcomposed of high-tenacity fiberglass yarn which is woven into a uniform,leno grid configuration. Another product, Polyfelt PGM-G® consists offiberglass rovings laid in a grid pattern onto a non-woven felt with thefelt meant to act as a water barrier to attempt to retard reflectivecracking.

Attempts have been made to use other tightly constructed structureswhich reinforce the roadway, but do not allow the passage of asphalticconcrete road materials through the reinforcing structure in the normalpaving process. Difficulties have arisen from using such tightlyconstructed reinforcement members in road construction. These tightlyconstructed reinforcement members create a barrier between the new roadoverlay and the old road or foundation restricting the passage throughor incorporation of asphaltic concrete materials into the reinforcementmember. This reduces the reinforcement benefits of the reinforcingmember and enables slippage or movement in the normal paving process.

Another family of products and structures which require reinforcementare concrete structures and other masonry or cementitious materials.These concrete materials have low tensile strength yet have goodcompressive strength. When using concrete as a structural member, forexample, in a bridge, building or the like, reinforcement is often usedto impart the necessary tensile strength. In new and existing concretestructures, such as precast driveways, slabs, sidewalks, pipe etc,reinforcement has been undertaken with a variety of steel shapes such asopen steel meshes, steel rebar, and steel grids. Steel grids have beenused in reinforcing concrete structures such as decking for drawbridges.These steel grids are a closed cell structure, and each section of steelgrid contains and confines a rectangular or square column of concrete.These types of grids are inherently very inefficient in their use of thereinforcing material.

Steel and other metals used as a reinforcing agent are subject tocorrosion. The products of corrosion result in an expansion of thecolumn of the steel which causes a "spalling" effect which can cause abreakup and deterioration of the concrete structure. This breaking andcrumbling of concrete structures are severe in areas of high humidityand areas where salt is used frequently on roads, driveways andsidewalks to melt ice or snow. Bridges over waterways in areas such asthe Florida coast or Florida Keys are exposed to ocean air which causesdeterioration and a short lifespan requiring constant rebuilding ofthese bridges. Concrete structures in the Middle East use concrete madewith the local acidic sand which also causes corrosion of steelreinforcements.

To replace traditional steel in reinforcing concrete, many types ofplastics have been considered. One attempted replacement for steel inreinforcement uses steel rebars coated with epoxy resin. Completecoating coverage of the steel with epoxy, however, is difficult. Also,due to the harsh handling conditions in the field, the surface of theepoxy coated steel rebars frequently will be nicked. This nickingresults in the promotion of localized, aggressive corrosion of the steeland results in the same problems as described above.

Fiberglass composite rebars have been used in reinforcing concretestructures such as the walls and floors of x-ray rooms in hospitalswhere metallic forms of reinforcement are not permitted. The method ofuse is similar to steel rebars. The fiberglass composite rebars havelongitudinal discrete forms which are configured into matrixes usingmanual labor. Concrete is then poured onto this matrix structurearrangement.

Fiberglass composite rebars are similar to steel rebars in that thesurface is deformed. Fiberglass gratings which are similar to steelwalkway gratings also have been used as reinforcements in concretes, buttheir construction, which forms solid walls, does not allow the freemovement of matrix material. This is due to the fact that the "Z" axisor vertical axis reinforcements form solid walls.

In dealing with reinforcing concrete support columns or structures,wraps have been applied around the columns to act like girdles andprevent the concrete from expanding and crumbling. Concrete is not aductile material, thus, this type of reinforcing is for only theexternal portion of the column. One type of wrap consists of wrapping afabric impregnated with a liquid thermosetting resin around the columns.The typical construction of these wraps has glass fiber in the hoopdirection of the column and glass and Kevlar fibers in the column lengthdirection. Another approach uses carbon fiber uni-directional (hoopdirection) impregnated strips or strands which are designed to be woundunder tension around deteriorated columns. The resulting composite iscured in place using an external heat source. In these approaches thematerials used in the reinforcing wraps are essentially applied to theconcrete column in an uncured state, although a prepreg substrate may beemployed which is in a "semi-cured" state, i.e. cured to the B-stage.When using a woven fabric, "kinking" can take place when using eithercarbon or glass fibers, because the weaving process induces inherent"kinks" in either a woven wet laminate or woven prepreg, which resultsin a less than perfectly straight fiber being wrapped around the column.

Another approach to reinforcing concrete structures and columns is toweld steel plates around the concrete columns to give support to theconcrete wall. Such steel plates are also subject to corrosion andloosening resulting from deterioration of the column being supported.This approach is only an external reinforcement and lacks an acceptableaesthetic appearance which makes it undesirable.

An approach to reinforcing concrete mixes has been using short (1/4 to1") steel, nylon or polypropylene fibers. Bare "E-type" glass fibers aregenerally not used due to the susceptibility of glass fibers to alkalineattack in Portland cement.

Thus, there is a need for improved structural members adapted toreinforce a variety of products. For example, there is a need for animproved structural reinforcement member for use in asphaltic concreteroadways. Additionally, there continues to be a need for a structuralreinforcement member for concrete structures which accomplishes thereinforcement or increases material properties of the concrete structurewithout being subject to corrosion or attack. There also remains a needfor methods to reinforce products using these structural members.

It is an object of the invention to overcome the deficiencies of theprior art as noted. A more particular object of this invention is toprovide a structural member adapted to effectively reinforce a varietyof different products. A further object of the invention is to providemethods for utilizing the structural member adapted to reinforce aproduct, and for efficiently producing the structural member.

SUMMARY OF THE INVENTION

The above and other objects and advantages of the present invention areachieved by the provision of a structural member adapted to reinforce aproduct and methods for utilizing the same as described herein. Oneembodiment of the invention comprises a gridwork comprising a set ofwarp strands and a set of weft strands disposed at substantially rightangles to each other, with each of the strands comprising at least onecontinuous filament, and with at least some of the strands of each setbeing spaced apart so as to define an open structure, and with thegridwork being impregnated substantially throughout with athermosettable B-stage resin so as to interlock the strands at theircrossover points and maintain the gridwork in a semi-flexible statewhich permits the gridwork to conform to the shape of the product to bereinforced. Thus with the gridwork in a semi-flexible state, the membercan be conformed to the shape of the product to be reinforced. The resinis curable in situ in the product to form a rigid composite by heatingto a predetermined temperature. The product is thereby reinforced withthe cured member within it.

Preferably, the sets of strands are non-interlaced, and in oneembodiment, the set of warp strands and the set of weft strands aresubstantially linear, so that the gridwork is generally flat. In anotherembodiment, the set of warp strands is corrugated into alternatingridges and grooves, and wherein the set of weft strands is substantiallylinear, so that the gridwork has a three-dimensional configuration.

Still another embodiment of the invention comprises a structural memberof the structure defined above, but which is instead impregnatedsubstantially throughout with a fully cured thermoset resin so as tointerlock the strands at their crossover points and maintain thegridwork in a relatively rigid state. This embodiment is particularlysuitable for use in reinforcing products made of Portland cementconcrete.

Another embodiment of the invention comprises a three-dimensionalstructural reinforcement member comprising a three-dimensional open meshgridwork as described used in conjunction with a generally flat opengridwork as described with the generally flat gridwork being positionedto be coextensive with one of the planes of the three-dimensionalgridwork. One particular embodiment of the invention comprises thisthree-dimensional structural reinforcement member impregnatedsubstantially throughout with a thermosettable B-state resin asdescribed previously so as to interlock the strands at their crossoverpoints and to retain the gridworks in a semi-rigid three-dimensionalconfiguration. Another particular embodiment of the invention comprisesthis three-dimensional structural reinforcement member impregnated witha fully cured thermoset resin so as to interlock the strands at theircrossover points and maintain the gridwork in a relatively rigid state.

Another embodiment of the invention comprises a method of structurallyreinforcing a product comprising the steps of providing an open meshgridwork as described above being impregnated substantially throughoutwith a thermosettable B-stage resin so as to interlock the strands attheir crossover points and maintain the gridwork in a semi-flexiblestate which permits the gridwork to conform to the shape of the productto be reinforced; applying the gridwork to the product; and thenapplying heat to the gridwork so as to cure the resin and convert thesame into a cured composite to thereby rigidize the gridwork andreinforce the product.

A further embodiment of the invention comprises a method of fabricatinga reinforced roadway composed of an asphaltic concrete materialcomprising the steps of preparing a foundation for the roadway;providing an open mesh gridwork as described above impregnatedsubstantially throughout with a thermosettable B-stage resin so as tointerlock the strands at their crossover points and maintain thegridwork in a semi-flexible state. Asphaltic concrete, which is heatedto a predetermined temperature is then applied upon the foundation, withthe gridwork embedded therein, and such that the heat of the asphalticconcrete acts to cure the resin in situ and convert the same into acured composite to thereby rigidize the gridwork and reinforce theasphaltic concrete.

Still another feature of the present invention involves an efficientmethod of producing a structural member of the described type, and whichincludes the steps of advancing the gridwork along a path of travelwhile

(1) immersing the advancing gridwork in a liquid resin which isthermosettable and capable of being heated to cure to the B-stage,

(2) guiding the resin coated advancing gridwork through a nip so as tosqueeze off excess resin, cause the resin to penetrate into the strands,and firmly press the crossover points of the sets of strands together,and then

(3) heating the advancing gridwork to an extent sufficient to cause theresin to cure to the B-stage without fully thermosetting.

The resulting gridwork with the B-stage resin may then be formed into asupply package, such as a supply roll, so that it may be convenientlytransported to the job site. At the job site, the gridwork is withdrawnfrom the supply package, conformingly applied to the product, and thenheated so as to cure the resin and convert the same into a curedcomposite and thereby rigidize the gridwork and reinforce the product.Where the gridwork is used to reinforce asphaltic concrete which isapplied to the roadway foundation in a heated condition, the heat of theasphaltic concrete acts to cure the resin, as described above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic environmental view of method of fabricating anasphalt or reinforced roadway composed of asphaltic concrete materialusing an open mesh gridwork which embodies the present invention.

FIG. 1A is a flow chart illustrating one embodiment of the method ofpreparing a reinforced roadway in accordance with the present invention.

FIG. 2 is a perspective view of a structural reinforcement membercomprising one embodiment of the present invention.

FIG. 3 is a perspective view of a structural member adapted to reinforcea product comprising another embodiment of the present invention.

FIG. 4 is a perspective view of a structural member adapted to reinforcea product comprising another embodiment of the present invention.

FIG. 5 is a perspective view of an embodiment of a structural member ofthe present invention and which is adapted for use with metal or fiberglass rebars;

FIG. 6 is a schematic illustration of a method of producing thestructural member in accordance with the present invention; and

FIG. 7 is a schematic illustration of a method of producing theembodiment illustrated in FIG. 3.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will now be described in detail hereinafter byreference to the accompanying drawings. The invention is not intended tobe limited to the embodiments described; rather, this detaileddescription is included to enable any person skilled in the art to makeand use the invention.

In FIG. 2, a structural reinforcement member for reinforcing a productis shown which embodies the present invention, and which comprises agridwork 10 comprising a set of warp strands 12 and a set of weftstrands 14 disposed at substantially right angles to each other. Each ofthe strands comprises a plurality of continuous filaments, composed forexample of glass, carbon, aramid, or nylon, with glass filaments beingthe most preferred. An E-type glass is particularly suitable.

The set of warp strands 12 is separated into groups 13, each containingtwo contiguous strands in the illustrated embodiment. The set of weftstrands 14 is separated into groups 15, each containing four contiguousstrands in the illustrated embodiment. The groups of strands of each setare spaced apart from each other so as to define an open structure.Also, it will be noted that in the illustrated embodiment, one strand ofeach group of the warp strands 13 lies on one side of the set of weftstrands, and the other strand of each group of the warp strands 13 lieson the other side of the weft strands. Thus, the sets of strands arenon-interlaced. Also, the resulting superimposition of the warp strandsachieves a "pinching or encapsulation" effect of the strands in the weftdirection creating a mechanical and chemical bond at the crossoverpoints.

The gridwork 10 is impregnated substantially throughout with athermosettable B-stage resin so as to interlock the strands at theircrossover points and maintain the gridwork in a semi-flexible statewhich permits the gridwork to conform to the shape of the product to bereinforced. The gridwork is designed to be incorporated into a finishedproduct such that the material is conformed to the shape or thefunctionality of the end-use product and then cured to form a structuralcomposite. The ability of the gridwork to be conformed to the shape ofthe product allows the member to be cured by the inherent heat that isapplied or generated in the ultimate construction of the finishedproduct. For example, in the case of laying hot asphalt in paving roadsor using hot asphalt for roofing systems, the thermosettable B-stageresin impregnated into the gridwork would be cured by the heat of thehot asphalt as used in these processes. The resin would be selected forimpregnation into the grid such that it would cure by subjecting it tothe hot asphalt at a predetermined temperature.

The crossover of the strands can form openings of various shapesincluding square or rectangular which can range from 1/2 to 6 inches ingrids such as that shown in FIG. 2. FIG. 2 shows a square opening withdimensions of 11/2 inches in the warp direction and 11/2 inches in theweft direction. The size of the glass fiber bundles in each strand canvary. A range of glass strands with a yield from 1800 yards per pound upto 56 yards per pound can be used. One preferred embodiment is havingeach group of warp strands 13 composed of two 247 yards per poundsuperimposed strands, and each group of weft strands 15 composed of fourside by side or overlapping strands of 433 yards per pound.

The gridwork 10 may be constructed using a conventional machine, such asthe web production machine disclosed in U.S. Pat. No. 4,242,779 toCurinier et al., the disclosure of which is expressly incorporated byreference herein.

FIG. 2 also shows the flat gridwork impregnated substantially throughoutwith a thermosettable B-stage resin so as to interlock the strands attheir crossover points and maintain the gridwork in a semi-flexiblestate. A B-stage resin is a thermosetting type resin which has beenthermally reactive beyond the A-stage so that the product has onlypartial solubility in common solvents and is not fully fusible even at150°-180° F. Suitable resins include epoxy, phenolic, melamine, vinylester, cross linkable PVC, and isophthalic polyester. A commoncharacteristic of all of these resins is that they are of the thermosetfamily, in that they will cross link into a rigid composite, which whenfully cured cannot be resoftened and remolded. They also have thecapability to be "B-staged", in which they are not fully cured and canbe softened and reshaped either to conform to the shape of the end useproduct or corrugated into a three dimensional shape as described below.The preferred embodiment will use a urethane epoxy resin applied to theflat open mesh scrim by means of a water emulsion.

A preferred method of producing the gridwork 10 includes applying theresin in a "dip" operation, as illustrated in FIG. 6. In particular, thegridwork 10 is produced on a continuous processing machine 20 asillustrated for example in the above-referenced '779 patent. From themachine 20, the gridwork 10 is advanced along a path of travel andimmediately immersed in a liquid resin bath 21 which is thermosettableand capable of being heated to cure to the B-stage. Next, the resincoated advancing gridwork advances through a nip defined by a pair ofsqueeze rollers 22, 24, which acts to squeeze off excess resin, causethe resin to penetrate into the strands, and firmly press the crossoverpoints of the sets of strands together. From the squeeze rollers, theadvancing gridwork is heated to an extent sufficient to cause the resinto cure to the B-stage without fully thermosetting. This heating isaccomplished by passing the gridwork through a radiant heater 26 or thelike, and then about a pair of heated cans 28, 29, so that heat andpressure from contact with the cans are applied to both of the surfacesof the gridwork. Finally, the advancing gridwork is wound into a supplyroll 30 so as to facilitate its transport to a job site, or to a furtherproduction operation as illustrated in FIG. 7 and described below.

In the above described "dip" operation, the resin in the bath 21 iswater emulsified with the water being evaporated by the subsequentnipping and heating operations. Resins which are capable of being"B-staged" as described above, are suitable, and the resins contemplatedfor this structural member are non-solvent based resins, and may or maynot be water emulsified. Resins such as polyethylene or PPS may also beutilized. These resins would be applied in an emulsion type coatingoperation, and cured to a B-stage.

Impregnating the gridwork 10 with a thermosettable B-stage resin permitsthe gridwork to be semi-flexible and conform to the shape of the productto be reinforced, particularly with the application of heat. Once thegridwork is conformed to the shape of the product to be reinforced, theB-stage resin is cured to a thermoset state, providing upon coolingadded rigidity and enhanced properties to the resulting product.

One of the advantages of the gridwork 10 as disclosed in FIG. 2 is thatit can be conformed to the shape of the product desired to be reinforcedand cured in situ using the heat available in the normal manufacturingprocess, such as heated asphaltic concrete in asphaltic roadwayconstruction. Alternatively, it may be cured by external heat, in whichcase it may be cured to a rigid state prior to incorporation into afinished product or supplemental heat can be applied after incorporationin the finished product, if desired.

Once cured, the gridwork is relatively rigid. This produces a structuralmember adapted to reinforce a product such as a pre-cast concrete part,base of asphalt overlay, etc. Such a rigid gridwork would bestructurally composed of the same strand configurations and compositionsas the flat gridwork impregnated with a B-stage resin, except that theB-stage resin has been advanced to a fully cured C-stage. The resultingrigid state of the gridwork provides added reinforcement to the product.

Another embodiment of the structural reinforcement member comprises athree-dimensional structural member as illustrated in FIG. 3 at 32. Thethree-dimensional structural member 32 may be formed by starting withthe flat gridwork 10 impregnated with a B-stage resin described aboveand processing it into a three-dimensional structure. More particularly,the set of warp strands 12 is corrugated into alternating ridges andgrooves, while the set of weft strands 14 remains substantially linear.As illustrated in FIG. 7, the gridwork 10 is withdrawn from the supplyroll 30 and heated by means of radiant heaters 34 or the like, whichserves to soften the B-stage resin and condition the material forcorrugation. The softened flat gridwork impregnated with a B-stage resinwill then be processed by a corrugating machine, such as meshingcorrugating rolls 36, 37 or a caterpillar pulling device of the typeused in the Pultrusion industry. The corrugating machine is preferablyheated to further soften the flat grid material and enable it to beformed into the three-dimensional structure, and convert the resin to afully cured C-stage if desired. Where full curing is desired, anadditional heating unit may be positioned immediately downstream of thecorrugating rolls, if necessary to achieve full curing. Upon exiting thecorrugating machine, the gridwork will be subjected to a cooling device38 at a predetermined temperature.

Subsequently, the gridwork will proceed through a roll-up mechanismwhich will roll up the corrugated material into a take up roll 39 suchthat nesting will occur to produce an acceptable roll for shipment tothe job site. The roll can be of a desired width or length toaccommodate the specific constraints of the product to be reinforced.

The three-dimensional structural member 32 can accommodate a variety ofparameters and grid configurations differing according to varying needsof different applications such as in concrete and asphalt roadconstruction. Grid height can be varied to accommodate restrictions ofend products. For example, grids for concrete will generally have agreater height than grids for asphalt paving primarily because of theneed to reinforce the greater thickness of a new concrete road ascompared to asphalt overlays which are usually only 2-21/2 inches thick.In a new asphalt road construction, where the thickness of the overlaymight be 5-11 inches, grids of greater height would be provided.Generally, asphalt is applied in asphaltic paving in a plurality oflayers each being 2-5 inches thick, and as such the preferred grid forasphalt reinforcement would have a height between 1/2 and 4 inches.Grids of varying width can also be provided, for example, grids up toseven feet are presently contemplated, yet no restriction is intended ongrids beyond this width by way of this example.

The three-dimensional structural member 32, with a thermosettableB-stage resin as described previously, permits the gridwork to besemi-flexible and conform to the shape of the product to be reinforced.Once the gridwork is conformed to the shape of the product to bereinforced, the B-stage resin would be cured providing added rigidityand enhanced properties to the resulting product. One of the advantagesof the gridwork as disclosed in FIG. 3 is that it can be conformed tothe shape of the product desired to be reinforced and cured in situusing either the heat available in the normal manufacturing process,such as heated asphaltic concrete in asphaltic roadway construction, orby heating from an external heat source. The structural member 32 couldalso be cured to a rigid state prior to incorporation into a finishedproduct if desired. The gridwork could be cured thermally at apredetermined temperature depending on the particular resin.

The three-dimensional structural member 32 has many potentialapplications. A preferred embodiment is a method for fabricating areinforced concrete or asphaltic roadway. Also, the three-dimensionalgridwork can be used for reinforcing concrete structures in concreteprecast slabs, for reinforcing double "T" concrete beams, concrete pipe,concrete wall panels, and for stabilization of aggregate bases such asrock aggregate used as a sub-base in road construction.

FIG. 4 shows another embodiment of a three-dimensional structuralcomposite member 40 adapted to reinforce a product, and which embodiesthe present invention. This embodiment comprises a three-dimensionalcorrugated member 32a which is similar to the member 32 as describedabove, but wherein the corrugations of the warp strands 12a are inclinedat about 45° angles, rather than substantially vertical as in the member32. Also, the number and placement of the warp groups 14a is different.As illustrated, the member 32a is used in conjunction with a generallyflat gridwork 10 as shown and described above in connection with FIG. 2.Specifically, the generally flat gridwork 10 is positioned to becoextensive with one of the planes of the three-dimensional gridwork.

The three dimensional composite member 40 can be impregnated with aB-stage resin as described above, or alternatively, it can be fullycured prior to incorporation into a product to be reinforced, such asPortland cement concrete products as further described below.

Another embodiment of the invention is illustrated in FIG. 5, andcomprises a three dimensional structural reinforcement member 32bcomprising gridwork of a construction very similar to that illustratedin FIG. 3, and which comprises groups of warp strands 13b and groups ofweft strands 15b disposed at right angles to each other. The member 32bfurther includes specific positions 42 molded into the warp strands ofthe gridwork to allow steel or fiber glass rebars 44 to be placed in atleast some of the grooves of the corrugations and so as to extend in thedirection of the corrugations. In the preferred embodiment, thesepositions would allow the steel or fiber glass rebars 44 to be placedbetween the upper and lower surfaces defined by the corrugations, andthus for example approximately 1 inch from the foundation or surfaceupon which the corrugated grid structure was placed. After placing thesteel or fiber glass rebars on these molded in positions 42, additionalsteel rebars (not shown) could be placed at right angles to the originalsteel rebars and on top of them holding them in place by tying them tothe "Z-axis" fibers of the composite corrugated gridwork. The mainbenefit to the "molding in" of the positions 42 into the corrugatedcomposite gridwork is to allow the steel or fiber glass rebars to beplaced a distance from the foundation or base upon which the corrugatedgridwork is placed. In placing steel rebars conventionally in productssuch as bridge decks, it is common to use small plastic chairs in orderto position the steel rebars so that they are not lying on thefoundation, but are positioned approximately 1-2 inch up off of thefoundation. These separate chairs are not required with the embodimentof FIG. 5.

Methods for Utilizing the Structural Reinforcement Member

The several embodiments of the structural reinforcement members asdescribed above can be utilized in a variety of methods for reinforcingvarious products. One method involves providing the gridwork impregnatedwith a B-stage resin as described, applying the gridwork to the productin conforming relation, and then applying heat to the product so as tocure the resin and convert the same into a fully cured resin to therebyrigidify the gridwork and reinforce the product. Any product where theadvantage of having a semi-rigid open reinforcement which could be curedin situ would be a potential application in which this method could beused. Therefore the embodiments contained herein by way of example donot limit such methods and uses.

There exist different methods to reinforce various products with theembodiment of this invention which comprises a generally flat gridworkimpregnated with B-stage resin, including methods to fabricatereinforced roadways, concrete structures, tires, and telephone poles.

One preferred embodiment of utilizing the generally flat structuralreinforcement member impregnated with a B-stage resin is a method offabricating a reinforced asphalt road overlay to stop or retardreflective cracking. FIG. 1 shows an embodiment of this method. Otherembodiments of the invention comprise methods utilizing thethree-dimensional composite structure impregnated with a B-stage resinor in the combination of the flat grid and the three-dimensional gridlaid coextensively with the three-dimensional grid structural member.Further, the three-dimensional gridwork structure can be provided, indifferent embodiments, with a corrugated configuration which defines twoparallel planes which are spaced apart a distance of between about 1/2and 6 inches as shown in FIG. 3. Another embodiment comprises a methodutilizing the three-dimensional structural reinforcement member in arigid state impregnated with a cured thermoset resin. Any of these openmesh gridwork configurations can be utilized in methods for fabricatingreinforced roadways by resurfacing old concrete or old asphalt roads orconstructing new asphalt roads.

FIG. 1 shows a method of fabricating a reinforced roadway 50 composed ofan asphaltic concrete material. Asphaltic concrete as used herein refersto road construction materials including an asphalt matrix material withaggregate (rock, etc.).

The method of fabricating a reinforced roadway 50 composed of anasphaltic concrete material comprises a first step of preparing afoundation 52 for the roadway. A second step comprises providing an openmesh gridwork of one of the above described constructions, such as thegridwork 10, and which includes a thermosettable B-stage resin so as tointerlock the strands at their crossover points and maintain thegridwork in a semi-flexible state. The third step comprises positioningthe gridwork 10 on the foundation 52 for the roadway, and the fourthstep comprises applying heated asphaltic concrete 54 upon the foundation52 so as to cover the gridwork, and such that the heat of the asphalticconcrete acts to soften the gridwork so that it can conform to thefoundation, and cure the resin and convert the same into a fully curedresin to thereby rigidify the gridwork and reinforce the underside ofthe asphaltic concrete overlay.

For the generally flat structural reinforcement member, the step ofpreparing the foundation of the roadway would preferably involveapplying an asphalt tack coat 56 to provide holding for the generallyflat grid. The step of providing the open mesh gridwork could beaccomplished by preferably unrolling the open mesh gridwork from supplyrolls 30 upon which the gridwork would be brought to the roadway. Thesesupply rolls could be used with both the generally flat orthree-dimensional structure. Various continuous lengths of the open meshgridwork impregnated with a B-stage resin could be contained on therolls in the circumferential direction around the rolls. The smalldiameter carbon or fiberglass strands are flexible enough to be appliedaround these rolls without cracking.

The gridwork could be unrolled onto the prepared roadway to a desiredlength and cut. The gridwork could also be cut to a desired specialtyshape and positioned on the road surface. The advantage of thesemi-rigid gridwork impregnated with a B-stage resin is that it can beprovided on rolls with varying lengths. The semi-rigid state allows thegridwork to roll without cracking or failing. Also, the semi-rigidgridwork resists wrinkling once placed on the foundation, allowingpersons or machines to move across it. The gridwork can be easily cutusing industrial scissors.

For the step of applying asphaltic concrete heated to a predeterminedtemperature, conventional methods of applying asphalt can be used. Infact, an advantage of the present invention is that in both the flatgrid and three-dimensional structure, conventional paving methods can beused. The asphalt paver would normally apply 2 to 21/2 inches thickasphalt overlay. Following this paver, a compactor would normallycompress the asphalt to the desired thickness.

The heat of the asphalt, which is approximately 200° to 300° F.,combined with the weight of the asphalt will cause the B-stage resin inthe gridwork to cure forming a cured composite on the bottom of theasphalt overly. There is also a mechanical bond of the cured gridcomposite to the base of the asphalt and a degree of a chemical bondbetween the B-stage thermosetting resin and the asphalt matrix material.The asphalt remains above 200° F. for at least an hour after initialapplication of the asphalt. B-stage resins which cure in this time andtemperature range are preferred for this embodiment.

The method of fabricating a reinforced roadway composed of asphalticconcrete material may further comprise the step of applying pressureupon the asphaltic concrete immediately after the applying step so as tocompact the same and generate additional heat.

The flat open mesh grid is un-rolled in the direction of travel of themachinery, such that as a continuous sheet, the grid will be less likelyto move during the process of laying the asphaltic road material. Thethree-dimensional gridwork structure is designed to deform sufficientlyunder the top layer of the packed asphalt under the weight of the pavingroller and not spring back up above the top of the paving after beingdeformed in the direction of the vertical Z-axis or produce internaldelamination in a horizontal plane. The three-dimensional structure hasthe added advantage over prior products as an open mesh product allowingthe asphaltic materials to pass through the grid and providethree-dimensional reinforcement to the new road overlay. The heat of theasphalt plus the weight of the asphalt cause the B-stage resin to cure.The three-dimensional gridwork can also be applied in a fully cured(C-stage) condition.

Once the flat grid with the thermoset resin is cured in situ to a rigidstate, the cured grid structure stabilizes and reinforces the immediatelaminate area between the bottom of the asphalt overlay and the oldconcrete road, or old asphalt road or in the case of the new asphaltroad would stabilize the interface between the asphalt and the preparedearth. If the cured gridwork is positioned between the top and bottom ofthe asphalt overlay, it would stabilize the interface of these twoseparately applied layers of asphalt. The cured grid would stabilize theimmediate surface of the bottom of the asphalt overlay or new asphaltroad, and it would increase the flexural, tensile and compressionstrength of this layer. The strands are disposed at substantially 90°angles such that the base of the asphalt overlay would be stabilized,diminishing or eliminating the tendency for reflective cracking topropagate up from a cracked old concrete or asphalt road would bedrastically diminished or eliminated.

The use of the flat grid and three-dimensional grid in conjunction, asshown in FIG. 4, would serve to unitize the three-dimensional compositegrid in the direction of corrugation and to allow workers in the fieldto be able to better walk on the material as the concrete is beingpumped through the grid structure to form the finished concrete road.The flat grid can be laid on top of the three-dimensional grid, andfastened with fastening means such as metal or plastic twist ties inorder to better hold the flat grid structure to the top of thecorrugated grid structure. Also, in concrete road construction a flatcomposite grid could be positioned beneath the three-dimensionalcorrugated grid structure to give added structural integrity to thethree-dimensional structure.

The three-dimensional gridwork is versatile in allowing the contractorto tailor the amount of desired reinforcement in the concrete road bynesting the corrugated three-dimensional structures one on top of theother. This would still allow concrete flow through the openings in thegrid structure, but would provide a means to increase the amount ofreinforcement in the concrete.

The three-dimensional corrugated grid structure will help prevent cracksfrom developing in the asphalt by reinforcing the asphalt roadbed inthree directions and will keep the roadbed surface flatter for a longerperiod of time by increasing the compression load carrying capabilitiesof the asphalt road. The vertical composite strands add to thecompression strength. The three-dimensional corrugated grid structure inasphalt road construction would allow "controlled" movement of theasphalt road in the direction of traffic flow, but would providecontinuous rigid reinforcement in the transverse direction to trafficflow which would stabilize the tendency of asphalt roads to expand inthe transverse direction as a result of the continued downward loads onthe "flexible pavement material". The preferred embodiment in asphaltoverlay of 2 to 21/2 inches of thickness is with a three-dimensionalcorrugated grid structure that is approximately 1 to 11/2 inches inheight.

The three-dimensional corrugated material could be supplied to theasphalt contractor on rolls. The corrugations would be transverse to thelongitudinal dimension of the roll, and this would allow nesting of theform as the product is rolled. The unrolling of the product onto theroadbed surface would also place the corrugations transverse to thedirection of vehicular flow. In order to apply this rolledthree-dimensional composite grid into an asphalt road, modification ismade to a standard asphalt paver such that a device for mounting a rollis positioned roughly in the center to the back of the asphalt paver.The corrugated material processes vertically behind the auger and infront of the compactor screed on a standard asphalt paver, so that it isapplied upon the roadway foundation concurrently with the asphaltconcrete. There is approximately a 3 inch opening which would besufficient to feed this roll of three-dimensional corrugated material.The material would come in contact almost immediately with the hot fluidasphalt mixture and lay down on the roadway being resurfaced or on theprepared surface in the case of new road construction. Due to the way inwhich the grid structure would feed, the bottom of the grid structurewould be in close proximity to the road surface and not up in theasphalt overlay. This method also has the advantage of laying down thegridwork behind the wheels of the paving machine, which permits agridwork having the full width of the paver to be laid down.

The three-dimensional structural member has numerous advantages. Oncepositioned into the asphalt overlay the asphalt road would be reinforcedto a greater degree than by prior art products. Also, the asphalt roadwould be stabilized in the transverse direction because only straight(non-corrugated) fibers will be positioned in this direction and thisplus the interlocking grid structure will reduce or eliminate thetendency of the asphalt road to expand in the transverse direction.Further, the composite strands in the "Z" direction will act likesprings. After being incorporated into the asphalt overlay, a very heavyroller compacts the asphalt. Typically a 3 inch thick asphalt overlaywill compact to 21/2 inches. The "Z" axis reinforcements are flexibleenough in order to bend into the shape of an arc as the compactor movesover the asphalt overlay. They are flexible enough to remain in a bentcondition and the cohesiveness of the asphalt mixture is great enough sothat the bent fibers do not cause the asphalt overlay to separate orshear horizontally under the upward pressure of the "Z" axis fibers.Once the asphalt has cooled, the composite grid is uniformly dispersedthroughout the asphalt overlay in which the "Z" axis fibers of thecomposite grid are in a bent condition and they will respond much like aspring as the road sees vehicular traffic from the standpoint ofproviding additional compressive load carrying capabilities.

In addition to the above explained reinforcement of the asphalt road inthe "Z" axis direction, the "Z" axis fibers will also move slightlyforward and back in the direction of vehicular traffic movement. This isa benefit to maintaining a smooth road surface where sudden vehicularstopping is encountered such as at a traffic light. Because thecorrugations are oriented to move forward and back in the direction ofvehicular traffic movement, and there are flexible composite "Z" axisoriented fibers, they will act as reinforcing springs to control thetendency of the asphalt road to move forward as a vehicle stops at atraffic light. They will move as the asphalt wants to move, but as theymove, they will generate a force in the opposite direction which willserve as a stabilizing force for the asphalt road to keep it smooth sothat it will not be moved forward permanently and produce a wrinkled,bumpy surface.

Composites especially fiberglass fibers reinforced with epoxy resins,have an established historical track record of performing excellently ina fatigue environment. In the case of the composites that are "bent" inthe "Z" axis, the continued very minor deflection that is seen asvehicles move over the road surface would not cause failure long term inthe composite "Z" axis structure.

The embodiments of the novel gridwork as described herein have a varietyof uses, in addition to reinforcing roadway surfaces. For example,decayed telephone poles can be rehabilitated, with the heat mechanismfor cure being a hot asphalt matrix or possibly additional external heatfor full cure. Another embodiment of the invention comprises a methodfor fabricating reinforced concrete columns with better performance inseismic regions with the heat cure provided by an external heater or bya hot asphalt matrix overcoat.

Another embodiment of the invention comprises a method for fabricating areinforced tire comprising calendaring an open mesh grid with a B-stageresin into a sheet of rubber, cutting the product and placing it in atiremold. During vulcanization of the rubber, the composite would becured into a structural composite laminate and be in the shape of thefinished product. A tire incorporated with this flat grid structurewould produce a structurally reinforced rubber tire. The fiberorientation of the grid would be such that the fibers would be orientedtransverse to the direction of the tire movement and also longitudinalto the direction of the tire movement. In a transverse direction, theimproved product would act like existing steelbelt radials and in thelongitudinal direction would have a tendency to keep the tire moreround. The reinforcements could be selected to make a stronger or moreflexible structure reinforcement which could influence the ride that isexperienced by the driver using tires made in this fashion.

The gridwork of the present invention, when fully cured as describedabove, is particularly useful in reinforcing a structure composed of aconcrete material, such as Portland cement concrete. For example, in thecase of new roadway construction, the foundation is prepared and thefully cured gridwork is placed upon the foundation. Thereafter, theliquid concrete is poured upon the foundation so as to immerse thegridwork, and upon the curing of the concrete, a reinforced concreteroadway is produced with the gridwork embedded therein.

Another use for the present invention involves a method of reinforcingasphaltic roofing, either as a prefabricated single-ply sheeting or as aconventional built-up roofing. During formation of the roofing, the heatof the hot asphalt will cure the B-staged resin to the C-stage. Theresult is a stronger roofing that will resist sagging or deformation andrupture by walking or rolling traffic on the roofing.

The present invention is more fully explained in the followingnon-limiting specific examples.

Resin Composition and Mixing Procedure

Weigh into an open topped 55 gallon drum 150 pounds of Epi Rez 3519-W-50(Shell Chemical). Add 150 pounds of Epi Rez 5520-W-60 to the same drumwith the Epi Rez 3519. Mix these two materials until uniformly blended.In a separate container weigh 4494 grams of 2 Methyl Imidazole (2MI) andadd 8989 grams of water. The water may be hot or cold. Heat this 2MI andwater until a clear solution is formed. The temperature should bebetween 75° C. and 85° C. (If heating is slow, additional water may beadded to replace evaporation losses.) Add the clear hot 2MI solution tothe rapidly stirred drum slowly over several minutes. The speed ofaddition should be adjusted to allow the 2MI to mix with the largervolume of water while remaining in solution.

The material is now ready to use. The viscosity can be adjusted by theaddition of water. Reduction of the viscosity to 2650 cps required theaddition of 6000 grams of water. Under normal conditions, this solutionwill be stable for about 3 days. The viscosity can be adjusted higher orlower to accommodate various machinery set ups to accomplish the desiredcoating of the roving.

First Specific Example of Gridwork

A gridwork may be fabricated in accordance with the method illustratedin FIG. 6, with the gridwork comprising

a) warp strands each composed of PPG 1715 roving composed ofapproximately 5,600 glass filaments, and each having a yield of about247 yards/lb; and

b) weft strands each composed of PPG 1715 roving composed ofapproximately 3,200 glass filaments, and each having a yield of about433 yards/lb.

The warp strands may be separated into groups each containing twocontiguous strands, with one of the strands lying on one side of theweft strands and the other strand lying on the other side of the weftstrands. The weft strands may be separated into groups each containingfour contiguous strands. The groups of strands may be separated so as todefine openings of 1-inch square.

The gridwork may be advanced so as to be immersed in a liquid resin bathformulated in accordance with the above specific example, and thenpassed through nip rollers to remove the excess resin and force theresin into the strands. The advancing gridwork may then be passedthrough a radiant heater, which serves to raise the temperature of thegridwork to about 150° F. and initiate the curing of the resin. Thegridwork may then be advanced over a pair of heated cans so thatopposite sides of the gridwork directly contact respective cans. Thecans should be heated to a surface temperature of about 428° F. Theresin will thereby be heated to an extent sufficient to cause the resinto cure to the B-stage without fully curing, and so as to interlock thestrands at their cross over points and maintain the gridwork in asemi-flexible state. The resulting product may then be wound into asupply roll.

Second Specific Example of Gridwork

A gridwork may be fabricated and wound into a supply roll as describedin the above example. The gridwork may then be withdrawn from the supplyroll and advanced through a radiant heater so as to heat the gridwork toa temperature of about 150° F. and thereby soften the resin. Next, theadvancing gridwork may be advanced through corrugating rolls which areheated to a temperature of about 250° F., and which serve to impartcorrugations of about 1 inch depth and 1 inch length to the warpstrands. The gridwork is then cooled, without having the resin changefrom its initial B-stage, and the gridwork may then be wound onto atake-up roll.

Third Specific Example of Gridwork

The gridwork of this example comprises a high warp unidirectionalB-staged non-woven grid using graphite fibers in the unidirectionaldirection, and is believed to be particularly adapted for reinforcingthe underside of damaged concrete structures such as bridge decks. Inthis product the unidirectional graphite fibers should be in closeproximity to each other (touching each other but not overlapping) with aminimal amount of cross-directional fiber. The amount ofcross-directional fiber should be sufficient to promote a degree ofcrossover fiber bonding so that the non-woven high unidirectional fabriccan be handled.

The resin may be a B-staged thermoset resin similar to the B-stagedthermoset resins used in other examples. Graphite fibers are preferredfor this application because in reinforcing damaged concrete structuressuch as bridge decks, graphite fibers have a much higher tensile modulusand will take loads quicker and provide a much more efficient andeffective fiber for reinforcing these deteriorated concreteapplications.

The method of applying this gridwork includes cleaning the area ofconcrete to which the gridwork is to be applied. After the surface ofthe concrete is cleaned, a layer of epoxy resin or epoxy glue may beapplied, followed by the positioning of the high unidirectional graphitefiber with the unidirectional graphite fibers in the direction wherethey would take the anticipated tensile loads. Additional thermosetepoxy resin or epoxy adhesive could be applied over the top of theunidirectional graphite non-woven gridwork in order to create a betterlaminate. The thermoset epoxy resin or epoxy adhesive generate a degreeof heat in the natural room temperature curing process, and externalheating devices such as heaters also could be used to applysupplementary heat to assist the thermoset resin or epoxy resin in itscuring as well as to promote a full cure of the unidirectional graphitenon-woven gridwork.

Fourth Specific Example of Gridwork Utility

The gridwork contemplated for this example comprises an open mesh gridstructure which may be impregnated with a B-staged thermoset resin, andwhich may be used for reinforcing "built up roofing structures". Broadlyspeaking, after the non-woven grid has been positioned with the othermaterials used in the roofing structure, hot asphalt which is normallyused in built up roofing structures to provide waterproofing andconsolidation of materials, may be applied so that the heat of theasphalt will promote the curing of the B-state thermoset resin in theopen mesh grid to produce the fully cured composite in situ with thebuilt up roofing system.

A wide latitude exists in selecting where the gridwork will be placed.Some possible examples are as follows:

a) The gridwork could be incorporated as a separate layer in the builtup roofing system, or

b) The gridwork could be combined in a secondary manufacturing operationwith the high density fiber glass insulation board on one or both sidesof the gridwork such that when applied in contact with the hot asphalt,curing would be promoted to provide a structural composite, load bearinglayer as part of the built up roofing system.

In this example there are many weights and grid opening patterns thatcould be selected for built up roofing systems, but the principle ofusing a non-woven gridwork that would cure in contact with the hotasphalt is a preferred feature which is common to all proposedembodiments.

In a built up roofing system, the cured gridwork system would providestability to the built up roofing system in both compression andtension. As the system would want to expand under the heat of the sun,the cured gridwork would provide tensile reinforcement to controlexpansion. At night time or in the winter when the built up roofingsystem would want to contract, the cured composite gridwork wouldprovide sufficient compression strength in order to stabilize the builtup roofing system, and minimize contraction. The overall effect ofminimizing contraction and expansion would be to significantly lengthenthe life of the built up roofing system by preventing cracking in theasphaltic material which is a direct result of excess expansion andcontraction.

In the drawings and the specification, there has been set forthpreferred embodiments of the invention and, although specific terms areemployed, the terms are used in a generic and descriptive sense only andnot for the purpose of limitation, the scope of the invention being setforth in the following claims.

What is claimed is:
 1. A method of reinforcing a structure composed of aconcrete material and comprising the steps ofproviding a gridworkcomprising a set of warp strands and a set of weft strands disposed atsubstantially right angles to each other, with each of the strandscomprising at least one continuous filament, with the gridwork beingimpregnated substantially throughout with a fully cured thermoset resinso as to interlock the strands at their crossover points and maintainthe gridwork in a relatively rigid state, wherein the sets of strandsare non-laced, wherein the set of warp strands includes a plurality ofstrands lying on one side of the set of weft strands and a plurality ofstrands lying on the other side of the set of weft strands, wherein atleast some of the strands of each set are spaced apart so as to definean open structure, and wherein the set of warp strands is separated intogroups each containing a plurality of contiguous strands, with at leastone strand of each group lying on one side of the set of weft strands,and at least one other strand of each group lying on the other side ofthe set of weft strands in contiguous superimposed relationship withsaid at least one strand, immersing the gridwork in liquid concrete, andpermitting the concrete to cure so as to produce a reinforced concretestructure.
 2. A method as defined in claim 1 wherein the immersing stepincludes placing the gridwork upon a foundation, and then pouring theliquid concrete upon the gridwork so as to immerse the gridwork.
 3. Amethod as defined in claim 1 wherein the gridwork is generally flat. 4.A method as defined in claim 1 wherein the gridwork comprises athree-dimensional structure.
 5. A method as defined in claim 4 whereinthe set of warp strands is corrugated into alternating ridges andgrooves, and wherein the set of weft strands is substantially linear, sothat the gridwork has a three-dimensional configuration.
 6. A method asdefined in claim 5 wherein the corrugated warp strands define parallel,generally flat, upper and lower surfaces, and wherein said set of warpstrands is shaped to define supports which are disposed within at leastsome of the grooves of the corrugations and which are configured tosupport elongate rears thereupon which extend in the direction of thecorrugations and are spaced between the upper and lower surfaces.